James DeMonaco’s “The Purge” operates on a premise that is so stupid that you feel like throwing rotten fruit at the screen. As you’re watching it, you hope that the screenplay will make up for its insipid ideas with a logical explanation, but no, this is one of those movies where all of the players end up running around in the dark shooting and killing one another in the manner of a video game. To our intense surprise, it can’t even get that right.

By now, you’ve heard the premise, which has been spilled out in endless ads running on television. In the year 2022 the United States is now controlled by a series of corporations known as “The New Founding Fathers of America”, who have devised an annual ritual so idiotic that no one can adequately explain it: Every year, on March 21st all crime is legal between the hours of 7pm and 7am – even murder. No police or medical services will be available. The government’s explanation (you’ll love this) is that they are trying to keep the population under control. They figure, given one night of violence, the populace will behave themselves for the other 364 days of the year. You could write volumes on the flawed reasoning behind this.

It hardly matters anyway because once that idea is set in place “The Purge” turns into an ugly, violent home invasion thriller centered on a nice family, The Sandins, headed by James (Ethan Hawke) and his wife Mary (Lena Headey). They have two kids, teenage daughter Zoe (Adelaide Kane) and young Charlie (Max), who loves surveillance. James has made himself rich by becoming the developer of a home security system that will protect wealthy families from the purge. The Sandins are convinced that they are safe, but having seen the trailer – and countless movies like this – we know this isn’t the case.

As the purge begins the family closes themselves inside the house behind thick sheets of metal which cover the windows and doors. A short time later, Charlie sees a homeless man on the surveillance camera wandering the street in front of the house. The man is bleeding and begging for shelter. The kid lets the man in, but soon his pursuers come calling, assuring James that they will get past his security system within the hour. What follows is a plot similar to David Fincher’s “Panic Room.” The difference is that that film used logic and characters to set up a unique cat and mouse game. “The Purge” uses creepy-masks, shotguns and bad editing to create phony jack-in-the-box terror. It recycles clichés, like having the family split up into different rooms so one person can emerge later in order to save another person who is about to be killed.

Somewhere in this insufferable mess, a message emerges about social justice and the tyranny of the “haves” over the “have-nots.” It eeks around the edges of the film but conveniently doesn’t get in the way of the repeated shots of someone getting blown to bits with a shotgun. This is an ugly, grimy little movie that comes down to a sick scene in which a mother painfully begs for her children’s lives while they have guns to their heads.

“The Purge” is a movie that gives you a lot of time to think. Ask yourself this: Why didn’t the Sandin’s just leave the country for the week of the purge? These are wealthy people, so why not just lock the house down and take a trip to Europe? Why not Canada? Or Australia, it’s supposed to be lovely this time of year.